The return of Masayo Imura, known as the "mother" of Japanese synchronised swimming, has bolstered the country's hopes ahead of this year's Olympic Games to such an extent the team will be considered "failures" if they return from Rio without a medal.

Japan won bronze when the team event was added to the programme at the 1996 Atlanta Olympics and took silver in Sydney and in Athens four years later. They also won duet bronze from 1984 to 1992 and silver in 2000 and 2004.

At the Beijing Games in 2008, Japan took bronze in the duet but failed to medal in the team event, while China, under Imura's guidance, finished third.

The Chinese then went one better in London with silver while Japan failed to make the podium in either category.

Imura's role in China's success prompted scathing criticism on social media for her "betrayal" of her homeland.

However, Imura returned home to take over as head coach in 2014 and the switch reaped immediate dividends. The Japanese took bronze at the World Championships in both team and duet events last year - success which captain Yukiko Inui said had jacked up expectations for Rio.

"Now we're in a position where if we don't take a medal, we've failed," Inui told reporters poolside after a recent practice session.

"So we're under a lot of pressure. The Olympics will be even tougher."

To prepare for Olympic preliminaries in Rio this March, the team - which usually train and compete indoors - underwent rigorous training in Guam to acclimatise to an outdoor pool for Rio.

"We practiced until we were satisfied," said Imura, who is known for her hard training methods.

"The swimmers had excuses written all over their faces: 'the wind is too strong' or 'the rain is so heavy we can't open our eyes' or 'the wind blew too suddenly.' Many excuses."

Imura's tough approach was on full display at the training session, where she paced poolside as the team swam and flipped in a routine based loosely on Japanese myths, occasionally shouting "No! You're doing it all wrong!"

While some athletes and visitors planning to come to the Olympics have expressed concern about Zika, a virus linked to birth defects in newborns, the Japanese swimmers did not seem overly concerned.

"Synchronised swimming athletes don't have the time to go out and relax in places like parks," Imura said though she added the team is getting information from Brazil on potential measures such as mosquito repellent.

Team captain Inui said the group was talking more about their routines and practice than Zika.

"We'll leave the worrying to our coaches and focus on what we do best," she added.